There are two basic approaches to mobilize the left colon and ligate the vessel, medial to lateral and lateral to medial. The medial to lateral approaches allow prompt mobilization and division of the main vessels proximally which is recommended by many experts in the cancer setting. There are two ways to do the medial to lateral mobilization: The first initiates dissection at the level of the sacral promontory whereas the second starts at the level of the inferior mesenteric vein (IMV). A brief description of each method follows.
Medial to Lateral Approach Starting at the Sacral Promontory
In the first method, the dissection is begun at the sacral promontory at the right base of the rectosigmoid colon. The surgeon stands between the legs with left hand in abdomen and right hand holding a bowel grasper through the left-sided cannula; the first assistant and camera person are on the patient's right side. The table is placed in the Trendelenburg position with the right side tilted down so that the small bowel will shift into the right upper quadrant. The surgeon may place a towel in the peritoneal cavity via the hand-assist device to pack the small bowel out of the way. The omentum is then swept cranially above the transverse colon to expose the mesentery.
The surgeon uses his hand to grasp the sigmoid mesentery and elevate it ventrally and to the left (Figure 9.1.3). This maneuver exposes the groove between the inferior mesenteric vascular pedicle and the retroperitoneum. The first assistant uses both right-sided cannulae; a grasper in one hand to facilitate exposure and a cutting device in the other. Using the endoscopic scissors, the first assistant incises the peritoneum immediately to the right and below the vascular pedicle. The incision starts at the sacral promontory and is continued a short distance both into the pelvis and toward the head to provide some working space. The surgeon then places his fingers underneath the vascular pedicle, and uses blunt dissection in order to lift the pedicle ventrally as well as to sweep the preaortic hypogastric plexus dorsally. The first assistant places the graspers underneath the cut edge of the incised peritoneum to help elevate the vascular pedicle and expose the retro-peritoneum. Blunt dissection is performed laterally until the left ureter and the gonadal vessels are visualized through this mesenteric window (Figure 9.1.4).
The peritoneum is further scored cephalad, just dorsal to the sigmoi-dal vessels on the medial aspect of the mesentery to the IMA level. The surgeon carefully grasps the artery with his hand, and continues blunt dissection posteriorly and laterally to reach the IMV. As the surgeon controls both of these vessels, the assistant incises the peritoneum across the pedicle to create a peritoneal window lateral to the vein. Both
Figure 9.1.3. In initiating the dissection of the IMA and IMV, the surgeon grasps the pedicle with the left hand and elevates it ventrally and to the left.
vessels should now be clearly exposed and retracted away from the retroperitoneal structures, making them ready for ligation (Figure 9.1.5). The artery and vein are then divided either proximal to or just distal to the left colic artery, depending on the preference of the surgeon. We prefer to ligate the vessels with an endoscopic coagulation device instead of with an endoscopic stapler or surgical clips (Figure 9.1.6). Blunt dissection continues posterior to the left colon mesentery, with the first assistant elevating the mesentery, and the surgeon's fingers sweeping, dorsally, the retroperitoneal fat and the anterior aspect of Gerota's fascia (Figure 9.1.7). Dissection should continue until the lateral attachments of the left colon are encountered at the splenic flexure. The correct dissection plane is avascular.
The next step in flexure takedown is separation of the greater omentum from the transverse colon. The surgeon initially grasps the transverse colon and retracts it caudally with the intracorporeal left hand while holding up the reflected omentum with a grasper held with the right hand, thus exposing the avascular attachments between these two structures (Figure 9.1.8). Starting at the mid-transverse colon, the assistant uses a grasper to improve exposure and a scissors to divide the avascular attachments and enter the lesser sac; once entered, the surgeon can place his fingers into the lesser sac in order to palpate, bluntly dissect, and expose the remaining attachments. After the omentum is separated, the colon should only be attached by the lieno-colic ligament and lateral attachments. The surgeon places his hand posterior to the colon mesentery and retracts the colon medially. Using
the endoscopic scissors in his right hand, the surgeon then divides the lateral attachments starting at the distal descending colon and proceeding cephalad. Division of the lienocolic ligament completes mobilization of the splenic flexure (Figure 9.1.9).
The alternate medial to lateral approach commences at the level of the IMV. Using this technique, the dissection is initiated cephalad to the IMA takeoff. The room and equipment setup as well as the position of the surgeon and assistants are the same as for the method just described. The table is placed in slight reverse Trendelenburg with the right side down. The back of the surgeon's intracorporeal hand is used to hold back the proximal ileum and the small bowel from the base of the descending colon mesentery, thus exposing the IMV and the ligament of Treitz. The surgeon's right hand grasps and elevates the descending colon which puts the mesentery on stretch. The first assistant grasps the left transverse mesocolon just beneath the bowel and retracts it upward with one hand, while using a scissors or other device in the other hand to score the peritoneum parallel to and a short distance from the IMV (Figure 9.1.10). This starting point is either just medial or lateral to the IMV depending on whether the vein is to be sacrificed or preserved. This opening is enlarged and a window created through
which the dissection can be initiated. Next, the plane between the posterior aspect of the mesentery and the anterior surface of Gerota's fascia is established through this window and continued laterally.
The hand and the laparoscopic instruments are alternately used to lift the mesentery upward, thus exposing the dissection plane, or to do the actual dissection. The cephalad extent of this mobilization is the inferior edge of the pancreas; the caudal limit is the left colic vessels. To continue the mobilization caudally, either the IMA (or the left colic vessels) must be divided or a new window created between the left colic vessels and the first sigmoid branch off the main sigmoidal vessel. The left ureter and gonadal vessels are then bluntly dissected down and away from the underside of the colonic mesentery as the dissection continues caudally toward the left iliac fossa (Figure 9.1.11). Next, the omentum is dissected away from the left half of the transverse colon. Then, as described earlier, the lesser sac is entered and the remaining flexure attachments are taken down. To complete the mobilization of the left transverse colon, the base of its mesocolon must be divided ventral to its insertion along the inferior border of the pancreas (Figure 9.1.12). Care must be taken to preserve the marginal vessels when performing this step. The final step is the division of the thin lateral peritoneal attachments of the descending colon.
The room setup and staff positioning are the same; the table is placed in mild reverse Trendelenburg with the right side tilted down and the omentum reflected cephalad. The surgeon, standing between the legs, grasps the descending colon with his left hand and retracts it medially
while using his right hand to initiate dissection by dividing the line of Toldt via the left-sided cannula (Figure 9.1.13). The first assistant uses two graspers to retract the proximal left colon and keep the small bowel and omentum out of the way. As the colon is detached, medial and upward traction by the hand must be increased. The proper dissection plane between the anterior aspect of Gerota's fascia and the underside of the mesocolon must be found; it is usually not evident at the start. Once the mobilization is well underway, the hand can be repositioned lateral to the colon; the back of the hand is used to retract the mesocolon (draped over it) medially and upward which exposes the proper (purple colored) dissection plane. The assistant holds the left colon out of the way. It is important to fully mobilize the descending mesocolon to a point medial to the IMV. Dissection proceeds toward the flexure and, if possible, the lienocolic attachments are divided.
Next, the omentum is separated from the left transverse colon as previously described (Figure 9.1.8). The intracorporeal hand, either left or right, is then used to identify the IMA and IMV. The mesentery can be displayed broadly by draping the colon over the surgeon's hand. The assistant then uses scissors to create windows in the mesentery between the vessels after which the artery and vein are ligated proxi-mally at the desired location. The bowel and remaining mesentery are next divided at the chosen level.
After completing the steps of: 1) The flexure takedown, 2) proximal devascularization, and 3) bowel division, there are two options. The first is to laparoscopically initiate the pelvic portion of the operation, whereas the second possibility is to commence the open part of the operation. It is the authors' impression that the open dissection, via a limited laparotomy incision, is facilitated by having fully scored the pelvic peritoneum laterally and anteriorly and also by establishing the presacral plane before ending the minimally invasive portion of the operation. Additionally, although unproven, it is again our impression that it is easier to identify and preserve the hypogastric presacral nerves laparoscopically.
The left monitor is repositioned lateral to the left foot or leg; the surgeon moves to the patient's right side and the first assistant to the left (Figure 9.1.1B). The patient is placed in Trendelenburg position and tilted right side down. This part of the case can be accomplished with the hand in or out of the abdomen. Provided the pelvis is sufficiently large, the assistant can grasp and retract the rectosigmoid upward with either the right or left hand. The remaining hand is used to provide and improve exposure. The surgeon using a grasper and a scissors then performs the dissection. The rectum and the surrounding structures and side-walls must be retracted and placed on tension in order to reveal the proper planes. Care is taken to identify and preserve the hypogastric nerves while establishing the proper plane that will permit full resection of the mesorectum (Figure 9.1.14). The initial lateral and anterior dissection can often be initiated laparoscopically without difficulty. Once the dissection has been fully commenced and the planes have been established, the open portion of the case should be initiated.
A variety of retractors are used to provide exposure through the limited incision including a Bookwalter or other table-affixed retractor and long hand held St. Marks or Deaver retractors. A final incision length of 9-12 cm is usually required and will vary depending on the surgeons' hand size and the body habitus of the patient. If not already done, the mobilized left colon is exteriorized and divided proximally with a linear stapler. Because the open rectal resection technique has been well described elsewhere, it will not be reviewed in detail here. Suffice it to say that a TME type mobilization is performed. Confirmation of lesion location and rectal washout with a tumoricidal solution
(9 : 1 dilution of standard 10% povidone solution with saline to obtain a final concentration of 1%) should be standard procedure before stapling and transecting the rectum. Full rectal mobilization as well as ligation and division of the mesorectum and the distal rectum are performed after which a double-stapled anastomosis via a transanally placed circular EEA device is accomplished. For distal rectal lesions, instead of stapling across the rectum, a rectal mucosectomy followed by a hand-sewn coloanal anastomosis may be necessary. Proximal diversion via a loop ileostomy may be warranted depending on the height of the anastomosis, a history of pelvic radiation, a positive leak test, and individual surgeon's judgment.
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